This invention relates generally to disposable rigid endoscopes for use in viewing a region within a body cavity. Endoscopes are optical instruments which are well known in the art, and are very useful in permitting the examination of body cavities without the need for extensive surgery.
Currently used rigid endoscopes are comprised of many optical lenses mounted in a tube to relay an image from inside a body cavity for viewing by a physician in order to diagnose various diseases or conditions. Since presently used lenses are made of glass that is ground and polished by conventional techniques, the cost of these instruments precludes disposing of the instrument after each surgery. Physicians desire to dispose of these instruments after each surgery to eliminate the risk of exposing the next patient to diseases such as AIDS or hepatitis. While most surgical instruments can be sterilized with high pressure steam, the delicate nature of the endoscope makes such sterilization difficult. Also, because of the fragility of these instruments, they are frequently broken, at great cost to the user.
A conventional endoscope includes a pipe for illuminating the region of the body to be viewed, and a lens system for focusing and relaying the image of the illuminated object. There are a number of disadvantages to prior art endoscopes which this and previous inventions have sought to overcome.
Referring specifically to U.S. Pat. Nos. 3,089,484 to Hett, 3,257,902 to Hopkins, 3,556,085 to Takahashi, 4,267,828 to Matsuo and 4,273,110 to Groux, Fantone, in his U.S. Pat. No. 4,784,118, pointed out that the prior art endoscope were complex and expensive to manufacture because of the use of carefully ground glass lenses. Fantone indicated that because of the high cost of glass lenses, endoscopes could not be made inexpensively, and therefore, disposable. In order to reduce the cost and complexity of the prior art systems, Fantone constructed an endoscope in which the light pipe, and the objective, relay, and viewing lens assemblies were all made of a polymeric material which lent themselves to injection molding. Such materials included acrylics, polystyrenes, polycarbonates and styrene-acrylonitrile (SAN) copolymers.
While the Fantone endoscope had some advantages over the prior art, the device had several problems. First, the plastic relay lenses were composed of only one material which increases the chromatic aberration of the image and reduces the resolution. In addition, in order to obtain a bright image, the plastic lenses have to be much longer than their diameters, and this is very difficult to manufacture using currently known manufacturing techniques.
To overcome these problems, I employ a hybrid system which incorporates glass plano cylinders disposed between molded plastic curved surface lenses which have a thickness on the same order of magnitude as their diameter. The plastic lenses can be made of two different types of plastic to allow for the correction of chromatic aberration. In order to achieve a bright image, the plano glass cylinders with flat polished end faces are placed in between the plastic lenses. In contrast to ground and polished lenses, the plano glass cylinders can be economically made in large quantities, while the smaller plastic lenses can be economically and accurately made by known injection molding processes. Therefore, my invention overcomes the major deficiencies of the prior art, while permitting the manufacture of a low cost, disposable endoscope.